Reflecting parabolic construction for solar heating systems

ABSTRACT

A reflecting parabolic construction for solar heating systems comprises at least a reflecting parabola for concentrating solar beams on a thermal carrier containing receiver tube, wherein the parabola comprises an aluminum fretted central layer, on the faces thereof two opposite aluminum layers are applied. According to a first embodiment, in the concave part of the reflecting parabolic construction a crystal mirror of minimum thickness is applied. According to a further aspect of the invention, one of the layers is a reflecting aluminum layer made by depositing vapors, and protected by a sol-gel protective layer having a thickness corresponding to few microns.

BACKGROUND OF THE INVENTION

The present invention relates to a reflecting parabolic constructiondesigned for concentrating solar radiations to be used in heatingsystems.

Systems exploiting different technologies or methods for collecting anconcentrating solar radiation are already commercially available.

The most diffused technologies relate to the linear paraboliccollectors, which are so designed as to cause the solar beams to beconverged toward a collector, including a diathermal fluid operating asa heat accumulator.

Prior methods or technologies, however, have not provided optimumresults, because of the need of making, for carrying out them, veryheavy and complex structures.

SUMMARY OF THE INVENTION

Accordingly, the aim of the present invention is to overcome the abovementioned problems, by providing a reflecting construction, to be usedin solar energy concentrating systems, which reflect construction has avery broad reflecting surface.

Within the scope of the above mentioned aim, a main object of theinvention is to provide such a construction of small weight and makingand installing cost.

Another object of the present invention is to provide such aconstruction which is very reliable and safe in operation and can bemade with any desired parabolic geometries or shapes.

Yet another object of the present invention is to provide such aconstruction which can be easily made and which, moreover, is verycompetitive from a mere economic standpoint.

According to one aspect of the present invention, the above mentionedaim and objects, as well as yet other objects, which will become moreapparent hereinafter, are achieved by a reflecting parabolicconstruction for concentrating solar radiation, characterized in thatsaid construction comprises a parabola including an aluminum frettedcentral layer having two opposite faces thereon are applied two oppositealuminum layers.

According to a first embodiment of the invention, to the concave part ofsaid parabola a crystal mirror having a very small thickness (less than1 mm) is applied.

According to a further aspect of the invention, one of the reflectingaluminum layers is made by depositing vapors and is protected by asol-gel protective layer having a thickness of few microns.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention willbecome more apparent hereinafter from the following detailed disclosureof a preferred, though not exclusive, embodiment of a reflectingparabolic construction, which is shown, by way of an indicative, but notlimitative example, in the accompanying drawings, where:

FIG. 1 is a schematic perspective view showing the reflecting parabolicconstruction according to the invention;

FIG. 2 shows a possible configuration of the subject constructionincluding supporting elements therefor; and

FIG. 3 is a schematic cross-sectional view showing the parabolic mirrorstructure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the number references of the above mentioned figures,the reflecting parabolic construction according to the presentinvention, which has been generally indicated by the reference number 1,comprises a plurality of linear parabolic mirrors 2, which extend for apreset length, thereby concentrating solar beams on a receiving tube 3holding a thermal carrier fluid therein.

In particular, the tube 3 is supported by supporting arms 4 forconnecting said tube to said linear parabolic mirrors and, moreover,said mirrors being in turn supported by rear brackets 10 allowing themto be coupled to supporting stands 11 for connecting to the ground.

Said parabolic mirrors are further connected to conventional drivingmeans, designed for changing the inclination of the mirrors depending onthe sun position in the sky.

The reflecting parabolic construction according to the present inventioncan be made at least in two different embodiments:

According to a first embodiment, the reflecting parabola comprises acentral aluminum fretted layer, on the opposite faces thereof areapplied two respective aluminum layers, a very small thickness (lessthan 1 mm) crystal mirror being further applied to the concave portionof the parabola.

The second embodiment consists of a reflecting parabola including acentral fretted aluminum layer, on the opposite faces thereof areapplied two further respective aluminum layers, one of which is made ofa reflecting aluminum material obtained by depositing vapors and beingprotected by a few micron thickness sol-gel material.

As clearly shown, the parabolic mirrors are made starting from alaminated material 20, including a central aluminum fretted portion 21,on the opposite faces of which are applied layers 22, also made ofaluminum.

According to the present invention, the reflecting surface 23 comprisesa colloidal suspension, adapted to solidify to a gel consistency.

The thus made porous product is chemically purified and heated to hightemperatures, thereby providing high purity oxides.

To the thus formed gel further doping substances are advantageouslyadded to provide the made glass like solid material with particularproperties, the set glass material practically providing a very thinmetal oxide coating.

The depositing is performed on the natural anodized aluminum of thelayers 22, by depositing vapors to a thickness from 0 to 10 microns,thereby providing a reflectivity with a reflection loss of maximum 2%.

Said colloidal suspension is so arranged as to practically provide avery thin layer, having a surface similar to a paint or glass material.

As is known the words “sol-gel” indicate a colloidal suspension adaptedto solidify to form a gel.

The thus made porous material is chemically purified and heated to ahigh temperature, for forming high purity oxides.

Also in this second embodiment it is possible to add other dopingsubstances, to provide the made glass like solid material, with desiredproperties, and depositing method is carried on a natural anodizedaluminum material by PVD technology (physical vapour deposition).

Within the receiving tube 3 a thermal carrier fluid is arranged.

As shown in FIG. 3, the top metal sheet 22 thereon the reflectingsurface 23 is applied, can be so perforated as to compensate thermalexpansions, to provide a reflecting parabolic device having very lightand highly functional construction.

The invention, as disclosed, is susceptible to several modifications andvariations, all of which will come within the scope of the invention.

Moreover, all the details can be replaced by other technicallyequivalent elements.

In practicing the invention, the used materials, as well as thecontingent size and shapes, can be any, depending on requirements.

1. A parabolic solar radiation reflecting construction for solar energyheating systems, comprising at least a reflecting parabola forconcentrating solar beams on a receiver tube containing a thermalcarrier fluid therein, characterized in that said parabola comprises acentral aluminum fretted layer having opposite faces on each of which isapplied a respective aluminum reflecting layer, said parabola having aparabola concave portion coated by a thin crystal mirror.
 2. Areflecting parabolic construction, according to claim 1, characterizedin that said aluminum layer is made by depositing vapors and isprotected by a sol-gel protective layer having a thickness of fewmicrons.
 3. A reflecting parabolic construction, according to claim 1,characterized in that said reflecting parabola has a reflecting surfaceincluding a colloidal suspension capable of solidifying to a gel form.4. A reflecting parabolic construction, according to claim 2,characterized in that said vapors are deposited on natural anodizedaluminum to a thickness from 0 to 10 microns, to provide said aluminumlayer with a reflectivity having a maximum reflectivity loss of 2%.
 5. Areflecting parabolic construction, according to claim 3, characterizedin that said colloidal suspension is deposited to a very thin colloidalsuspension layer with a surface similar to that of a paint or glassmaterial.
 6. A reflecting parabolic construction, according to claim 4,characterized in that said natural anodized aluminum is treated by aphysical vapor deposition method.
 7. A reflecting parabolicconstruction, according to claim 1, characterized in that saidconstruction comprises a top metal sheet element coated by a reflectingsurface and comprising a plurality of holes for compensating thermalexpansions.